A fluorescent colorimetric pH sensor and the influences of matrices on sensing performances.

A fluorescent colorimetric pH sensor was developed by a polymerization of a monomeric fluorescein based green emitter () with a monomeric 2-dicyanomethylene-3-cyano-4,5,5-trimethyl-2,5-dihydrofuran derived red emitter () in poly(2-hydroxyethyl methacrylate)--polyacrylamide (PHEMA-co-PAM) matrices. Polymerized () in the polymer matrices showed bright emissions at basic conditions and weak emissions at acidic conditions. Polymerized () in the polymer matrices exhibited a vastly different response when compared to . The emissions of are stronger under acidic conditions than those under basic conditions. When and were polymerized in the same polymer matrix, a dual emission sensor acting as a ratiometric pH sensor () was successfully developed. Because the and exhibited different pH responses and separated emission windows, the changes in the emission colors were clearly observed in their dual color sensor of , which changed emission colors dramatically from green at pH 7 to red at pH 4, which was detected visually and/or by using a color camera under an excitation of 488 nm. In addition to the development of the dual color ratiometric pH sensor, we also studied the effects of different matrix compositions, crosslinkers, and charges on the reporting capabilities of the sensors (sensitivity and p).